This invention relates to thermoplastic polyesters and to articles prepared from such polyesters.
Polyesters such as polyethylene terephthalate are used commercially in the packaging of various materials such as seasonings, carbonated beverages, detergents, cosmetics, etc. See, "Thermoplastic Polyester Resins for Containers" D. P. Callander, Polym. Sci., 25(8), 453-457(1985). While polyethylene terephthalate exhibits adequate gas barrier properties for containing some materials, it is inadequate for containing and storing such materials as beer, wine and low-acid foods such as meats or vegetables.
In order to improve the barrier properties of these polyesters, it has been recently learned to use hydroxyphenoxyether polyalkylene terephthalates and other hydroxyphenoxyether esters in packaging applications requiring improved barrier. --See, for example, Japanese Patent Shutsugan Kokai No. 62-25151. While such polymers exhibit improved barrier properties, they are generally used in blends with other polymers because, in neat form, they undergo crosslinking when extruded or otherwise processed at temperatures above their glass transition temperatures.
In view of the limited barrier properties of the polyethylene terephthalates and the poor thermal processability of polyesters having pendant hydroxyl moieties and phenoxyether moieties, it would be highly desirable to provide a polymer having good thermal processability and a genuinely high barrier (i.e., oxygen transmission rate less than 2.0 cm.sup.3 -mil/100 in.sup.2 -atm-day) to oxygen. Polymers that retain such high barrier in both dry and moist environments would be especially desirable.